This invention relates to a control system for a clutch disposed between an engine and a transmission mounted on an automotive vehicle.
In order to facilitate the driving of automotive vehicles, automatic transmissions have been developed and put into use in which a conventional friction clutch or counter-shaft gear-type transmission is utilized and engagement/disengagement of the friction clutch or a speed change in the transmission is controlled by an electronic control unit using a microcomputer.
A control system which decides a target position of an amount of clutch engagement in an automatic transmission using such an electronic control unit has been disclosed in the specification of Japanese Patent Application Laid-Open (KOKAI) No. 63-61644 and includes a load sensor for sensing engine throttle opening, an engine rotation sensor for sensing the rotational speed (rpm) of the engine, an input shaft rotation sensor for sensing the rotational speed of the input shaft of a transmission, and a clutch actuator which controls the engagement of a friction clutch, wherein maps associated with these three sensors are retrieved based on signals from the sensors serving as information indicative of the vehicle load, the corresponding amount of clutch engagement is obtained and the clutch actuator is driven accordingly.
When a vehicle equipped with an automatic transmission for controlling a disk clutch in accordance with the foregoing proposal is parked in a lot or at a curb, the friction clutch will not grip. For this reason, the vehicle is controlled at very low velocity by stepping down on the accelerator pedal and foot brake in very small amounts. When a load is carried in and out by a truck or the like, it is necessary for the truck to make small movements on the order of several centimeters relative to a loading platform. In such case the driver must quickly alternate between the accelerator pedal and brake pedal. If there is a delay in switching from one pedal to the other, the vehicle may contact the platform or some obstruction and sustain damage.